Up to now, drawings printed on paper are used in a building site, a civil engineering site, and the like, but an enormous number of sheets of drawings may be used, and it is burdensome for a user to carry around the drawings printed on the paper and perform work using the printed drawings.
Therefore, attention is being focused on a tablet-type image display device that allows drawing data for printing on paper, which is managed in a drawing database or the like, to be carried around easily. The tablet-type image display device has a disadvantage in that a display screen thereof is far smaller than the printed drawing used on site.
In contrast, by using various functions of a terminal device such as enlargement and reduction of the drawing being displayed and movement (scrolling) of a display region thereof, even when an image (drawing) having a large size such as A0 size and A1 size is handled, a tablet-type display terminal having only a screen area of a fraction of the image (drawing) can be used to display and view the image (drawing). In addition, there is an advantage in that the image can be displayed to be larger than the printed drawing depending on an enlargement ratio.
However, a tablet-type drawing display device is advantageous in having an enlargement ability, whereas it may be hard to recognize which portion of the entire image (drawing) is being enlarged and displayed at a time of the enlargement.
For example, in an architectural drawing, center lines for columns and walls may be displayed as base lines, and each of the base lines may be denoted by a base line number, the base line number being generally described around the drawing, for example, on the left, right, top, or bottom thereof.
Accordingly, there is a problem in that, when a location apart from the base line number is enlarged and displayed, it is impossible to grasp the base line numbers for the walls and the columns that are being displayed.
In order to solve the above-mentioned problem, Patent Literature 1 proposes a technology for setting a region including the base line number within entire image data as a guide image region and displaying a main body image region and the guide image region that are cut out from one entire image data.